The present invention relates to mixing machines, and relates more particularly to such a mixing machine in which two transmission sleeves are coaxially mounted around a spindle in a hole on the container cover and driven to turn respective mixing blade assemblies in reversed directions.
When making an emulsifying product for example a hair lotion or ointment, powder material and liquid material are put together and then mixed in a mixing machine into an emulsifying condition. Various mixing machines have been disclosed for this purpose. In order to prevent air from being mixed with materials, materials must be mixed in a mixing container which is maintained in a vacuum status. The mixing blade unit of a mixing machine for mixing materials in a mixing container having no air in it, is generally comprised of three mixing heads. One of the mixing head is suspending in the mixing container near the bottom and coupled to a bottom transmission shaft, which is inserted through a hole in the bottom side of the mixing container and driven by a motor, which is disposed below the mixing container. The other two mixing heads are disposed below the container cover and coupled to a top transmission shaft, which is inserted through a hole in the container cover and driven by a motor, which is disposed above the container cover. When materials are put in the mixing container, the container cover is closed on the mixing container, then air is drawn away from the mixing container, and then the top transmission shaft and the bottom transmission shaft are simultaneously driven to turn the mixing heads, permitting the materials to be mixed into an emulsifying condition. Because the bottom transmission shaft is inserted into the mixing container from the bottom side to hold one mixing head inside the mixing container, it is difficult to clean the inside of the mixing container during a maintenance work. When to pour well mixed substance out of the mixing container, the mixing container with the bottom transmission shaft and the related motor must be simultaneously turned about the horizontal pivot means on which the mixing container is mounted. Because the whole assembly of the mixing container, the bottom transmission shaft and the related motor is heavy, it is not easy to pour well mixed substance out of the mixing container. Because the mixing heads are not disposed in contact with the inside wall of the mixing container, materials tend to be adhered to the inside wall of the mixing container. When the inside wall of the mixing container is covered with a layer of emulsion, the cleaning work becomes more difficult. Furthermore, in regular mixing machines, the container cover is fastened to a horizontal suspension arm, which is suspended above the machine base and moved vertically relative to the machine base by a lifting mechanism. When the horizontal suspension arm is moved up and down relative to the machine base, the bellows tube which is coupled between the horizontal suspension arm and a vacuum pump in the machine base tends to be stretched and damaged. If the bellows tube is ruptured, air cannot be effectively drawn away from the mixing container. Furthermore, before opening the container cover, the inside pressure of the mixing container must be released. Therefore, a release valve means must be installed. However, the installation of a release valve means complicates the structure of the mixing machine, and relatively increases the manufacturing cost of the mixing machine.